1. Field of the Invention
The present invention relates to a process for the determination of an LDH.sub.1 fraction in a sample.
2. Description of the Related Art
LDH (lactate dehydrogenase) has five isozymes, that is LDH.sub.1 through LDH.sub.5. Each of organs has its own composition of the isozymes. For example, LDH.sub.1 is present in a myocardium in the largest amount. Since LDH.sub.1 escapes from the myocardium into blood under a condition of a myocardial infarction, a rise in serum LDR.sub.1 level can be diagnostic for such a disease. Therefore, an LDH.sub.1 isozyme assay is clinically significant.
In a most common LDH isozyme assay, LDH.sub.1, LDH.sub.2, LDH.sub.3, LDH.sub.4 and then LDH.sub.5 are fractionated in the order of electrophoretic mobility. An immunological LDH assay is also known. In other LDH assay disclosed in Japanese Patent Publication No. 6477/1983, a coenzyme derivative (e.g. reduced type nicotinamide adenine dinucleotide) is used. In addition, LDH assays wherein a sample is treated under an alkaline condition are described in Japanese Patent Publication No. 28280/1985 and Japanese Patent Kokai Publication No. 278997/1987.
The above-mentioned electrophoretic or immunological assay is unsuitable for clinical autoanalysis because of complicated process and long operation time. In addition, the LDH isozymes may be insufficiently fractionated by the electrophoretic method.
Strictly speaking, it is impossible to assay the LDH isozyme fractions by the method wherein the coenzyme derivative is used, while the ratio of H subunit to M subunit in the enzyme can be suitably determined by the method.
In the method comprising the alkaline treatment of the sample, more than 50% of LDH.sub.1 may be inactivated during the inhibition of the other isozymes. In addition, the process is complicated and takes a long time.
Thus, the above-mentioned conventional LDH assays are unsatisfactory for a clinical examination.